Electroconductive laminates having transparency are used as a transparent electrode of e.g. a liquid crystal display device, a windshield for an automobile, a heat mirror, an electromagnetic wave shielding window glass, etc. For example, Patent Document 1 discloses a coated electroconductive laminate comprising a transparent substrate, and a transparent oxide layer comprising zinc oxide and a silver layer alternately laminated on the substrate in a total layer number of (2n+1) (wherein n is an integer of at least 1). Such an electroconductive laminate is described to have sufficient electrical conductivity (electromagnetic wave shielding properties) and visible light transparency. However, if the lamination number n is increased to increase the number of silver layers so as to further improve electrical conductivity (electromagnetic wave shielding properties) of the electroconductive laminate, the visible light transparency tends to decrease.
Further, an electroconductive laminate is used also as an electromagnetic wave shielding film for a plasma display. Since electromagnetic waves are emitted from the front of a PDP, for the purpose of shielding the electromagnetic waves, an electromagnetic wave shielding film comprising a substrate such as a plastic film and an electroconductive film formed on the substrate is disposed on the observer side of a PDP.
For example, Patent Document 2 discloses a protective plate for a plasma display comprising, as an electroconductive film, a laminate having an oxide layer and a metal layer alternately laminated.
An electromagnetic wave shielding film is required to have a high transmittance and a low reflectance over the entire visible light region, i.e. to have a broad transmission/reflection band, and to have high shielding properties in the near infrared region. In order to broaden the transmission/reflection band, the number of lamination of the oxide layer and the metal layer should be increased. However, if the number of lamination is increased, such problems arose such that the internal stress of the electromagnetic wave shielding film increases, whereby the film curls, or the electroconductive film may be broken to increase the resistance. Further, if the number of lamination is increased, the visible light transparency decreases in some cases. Thus, heretofore, the number of lamination of the oxide layer and the metal layer in the electroconductive film has been limited, and an electromagnetic wave shielding film having a broad transmission/reflection band even in a small number of lamination and having excellent electrical conductivity (electromagnetic wave shielding properties) and visible light transparency has not been known.
Patent Document 1: JP-B-8-32436
Patent Document 2: WO98/13850